In the past floating dry docks have been created by the assembly of a number of identical floating subunits. These units have been roughly cubical with tabs projecting from the vertical edges at or near the horizontal midline. By fastening adjacent tabs to each other, a floating dock with a substantially flat deck surface of any desired configuration could be assembled.
Examples of such units and docks assembled from such units are found in U.S. Pat. Nos. 3,824,664 and 4,604,962. These patents describe hollow cubical units which in practice have been manufactured about 16 inches on a side. The units have been molded from a suitable plastic material with the tabs which project from each vertical edge positioned so that a dock of virtually any shape with a flat deck or top surface could be formed. The units have also been provided with bungholes so that the units could be partially flooded to lower the water line of some or all of the units. This has been done particularly where the dock has been used for personal watercraft.
With a personal watercraft, such as a jet ski, or with other small craft, such as a motor boat or jet boat under about 18 feet in length, the goal of the floating dry dock has been to make it possible to drive the craft up onto the dock. This would enable the driver to get on and off the craft without getting in the water and would also permit the craft to be stored out of the water.
Attempts to accomplish these goals have not been entirely successful. The dry docks assembled from prior art units have been either too high above the water to permit a personal watercraft to be driven on, or too low to keep the driver and craft out of the water entirely. Keeping the craft high and dry when not in use is important to protecting the machinery of the craft. In addition, the surfaces of the dock which the craft slides over must be ordinarily above the water line, otherwise marine growths, such as barnacles, will develop and scratch the smooth bottom surface to the craft, doing damage each time the craft slides onto or off of the dock.
The prior art has also included floating units like those shown in the patents identified above, but shorter. These units were about 16 inches square in plan view, but only about 10 inches tall. In addition, in these shorter units the tabs were still about 8 inches down from the deck surface and correspondingly closer to the bottom surface. These shorter units have been thought useful for assembling docks for light watercraft such as the shells used by college crew teams.